The conventional Public Switched Telephone Network (PSTN) is a circuit switched network in which calls are assigned dedicated circuits during the duration of the call. Such networks are well known in the art, and service providers have developed various services which may be provided to subscribers via such a conventional circuit switched network.
Recently, data packet networks, such as local area networks (LAN) and wide area networks (WAN) have become more prevalent. These data packet networks operate in accordance with the Internet protocol (IP) and such networks are referred to as IP networks. The popularity of IP networks has created an interest in providing voice and related services over IP networks.
Conventional PSTN voice services dedicate a circuit connection between a calling and called party, and as such, that connection is guaranteed a certain level of performance because it is not shared with any other network users. IP networks, on the other hand, are shared networks in which the network resources are shared between users. The notion of a connection in a data packet network is very different from the notion of a connection in a circuit network. In a circuit network, the connection is a dedicated circuit which is used only by the calling and called parties. As such, it is easy to guarantee a certain level of service via the circuit network. The problem with such a network is that of efficiency. That is, the dedication of a circuit between all calling and called parties may be inefficient because such dedicated circuits provide more bandwidth than is necessary. In a data network, the connection between two parties is not dedicated; and traffic between the parties is transmitted via the data packet network along with the data packets of other users. There is no dedicated path between the parties, and data packets may be transmitted between the parties via different paths, depending upon network traffic.
One of the difficulties with providing voice and other services over an IP network is that certain services require a minimum guaranteed level of service. For example, in order for a voice over IP (VoIP) call to provide an acceptable level of service, the connection must provide a certain bandwidth so that voice quality is acceptable. Other related services (e.g., data, video) also require a minimum guaranteed level of service in order to be acceptable. As IP network traffic increases, the network may become congested, and as such, the services provided via the network may become degraded.
Network congestion may be the result of the network elements becoming overloaded. For example, if the load on a network element becomes greater than its processing capability, then an overload condition may be reached at the network element. Such an overload condition could result in degraded performance and network services provided in connection with the network element may be adversely impacted. A serious problem occurs when the service provided by the network falls below a required minimum guaranteed level of service.
What is needed is a technique for controlling network congestion resulting from an overload condition at network elements.